Shipping and Import Taxes

The formula for shipping and import_tax is:

shipping (per box of 6) + import_tax (per bottle)

... shipping * (roundup (number_of_bottles / 6))              +            import_tax * number_of_bottles 

Shipping price is per box of 6 = shipping + fees for forwarder (local shipping by fulfilment agent)

Shipping price is determined by province_id.

This shipping scheme “penalizes” purchases for units less than 6. 

Although the shipping expense of sending 1 bottle can be less than 6 bottles (less weight and volume), it adds handling costs (manually repackaging fewer bottles in a box). So, to keep it simple, shipping costs are the cost of shipping boxes of 6, independent of the number of actual bottles in the box. 

12-bottle shipping?

Doesn't this model restrict us to 6-pack packages?

Not really...but since shipping is dependent on weight, it works out to be a useful metric. So if someone is ordering 2 bottles, and we need to repack this (from a 12-pack)this is going to incur some handling costs, but will have much less weight for shipping...so basing everything on a 12-pack shipping fee would be exorbitant. 

import_tax = import duties (importer landed price per bottle includes import duties and international shipping and insurance)

So, if someone in Argentina orders:

1 bottle = shipping price (box of 6) + import_tax (1 x $0)

6 bottles = shipping price (box of 6) + import_tax (1 x $0)

9 bottles = shipping price (2 boxes of 6) + import_tax (1 x $0)

in someone in Spain:

1 bottle = shipping price (1 box of 6) + taxes (1 x $5)

6 bottles = shipping price (1 box of 6) + taxes (6x $5)

9 bottles = shipping price (2 boxes of 6) + taxes (9 x $5)